WASHINGTON — The director of the FBI said Thursday that U.S. agents are already in Moscow and Sochi to assist with security measures for the upcoming Winter Olympics, but emphasized that “it’s a Russian responsibility” to ensure the Games go off without any attacks or disruptions.

James Comey said “a couple of dozen” FBI personnel are in place in the Russian capital and a “smaller number” are in Sochi, where the Winter Olympics are scheduled to get underway next month. He indicated that their focus is on protecting U.S. athletes.

He said that U.S. and Russian cooperation over security matters has been going “well,” despite recent bombings that have prompted Russian authorities and President Vladimir Putin to step up their own security measures. That international cooperation appears to be an improvement; last year the Kremlin was resisting U.S. offers of security help at Sochi, and their refusal became a source of friction, analysts said then.

Comey, speaking to a group of reporters at FBI headquarters in Washington, also said his agency was “deeply involved” in preparing for the NFL's Super Bowl in the New Jersey Meadowlands. He said the FBI field office in Newark, N.J., was taking the lead in assisting local and state police in preparing for the football championship.